Pulse March2011

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<p>HI</p> <p>GH</p> <p>-POWERED R ES E</p> <p>A</p> <p>R</p> <p>C</p> <p>H</p> <p>FOR</p> <p> March2011Issue 1 VacuumCircuitBreaker ModelinPSCAD/EMTDC 4 SinglePhaseAuto-reclosingand SecondaryArcConsiderations 7 KineticTurbinePowerConverter 0 2010PSCADUserGroupMeeting 1 1 NewandImprovedPSCADForum 1 2 PSCAD2011TrainingSessions 1</p> <p>TH</p> <p>E REAL WOR</p> <p>March 2011</p> <p>VacuumCircuitBreakerModelinPSCAD/EMTDCOlof Karln, Karln Engineering ThisapplicationnotepresentsaVacuumCircuit Breaker(VCB)modelanditsimplementationin PSCAD/EMTDC .Thismodelinvestigatestheability ofthebreakeroncurrentchoppingbeforecurrent zero,itsdielectricwithstandforTRV(Transient RecoveryVoltage)andhighfrequencycurrent quenchingforre-ignitionacrossthebreakercontacts. Anarcisdevelopedbetweenthecontactsandthe currentcontinuestoflowuntilthepre-setchopping levelisreached.Thispre-setlevelishighlydependent ofthecontactmaterialintheVCB.Whenthechoppingtakesplace,BRKchangesstatusfromclosedto openandthecurrentisforcedtozero.Theenergy preloadedintheinductancesurroundingthe breakeristransferredtocapacitanceinthecircuit.</p> <p>TheVCBismodelledbytheuseofthestandardPSCAD TheresponsefromthecircuitisaTRVthatincreases singlephasebreakermodelwithitsabilitytochange betweenthecontacts.Ifthemechanicalopening electricalswitchingstatusbycontrollingthebreaker timetopenisclosetotchop,thecontactseparation parameterBRK. willbeonlyslightatthechoppinginstant.Hence, thevoltagewithstandwhichhasbeenbuiltup betweenthecontactsisnothighenoughtoensure currentinterruption.WhentheTRVreachesthe voltagewithstandcharacteristics,are-ignition occursbetweentheVCBcontacts. Whenthehighfrequencycurrentisclosetozero, theVCBhastheabilitytobreakthecurrent.The Tosimulatecurrentchoppingandre-ignition,asimple slopeatcurrentzeroismeasuredandcompared tothecurrentquenchingcapabilitythathasbeen singlephasetestcircuitisestablished.Thecircuitis developedbetweenthecontacts.Ifthecurrentslope representingasinglephasetransformerwhichis islessthantheseparticularcharacteristics,thecurrent switchedoffbytheVCB. isquenched.TheresultingTRVisveryfastrisingand reachestheelectricalwithstandcharacteristicsquickly. Acircuitbreakersbreakingsequenceisactivatedby openingthebreakermechanically.Thisisaccomplished Asaresult,anewre-ignitiontakesplacebetweenthe contactsandahighfrequencycurrentstartstoflow. byanimpulsetrainthatfreezesattheinstantofthe mechanicalopeningofthebreaker.Thisisthestarting ThissequenceisrepeateduntiltheTRVdoesnot reachtheelectricalwithstandcharacteristics. pointforseparationofthecontacts.Agenerally acceptedapproximationforcontactseparationin VCBsisconstantspeedduringthefirstmillimetre ofseparation.Figure1 ThetestcircuitfortheVCBinPSCAD</p> <p>LD</p> <p>DielectricandQuenchingCapabilityCalculation Thewithstandvoltageisafunctionofthecontact distance.Itcanbeconsideredtobelinearlydependent forthefirstmillimetreofthecontactseparation.That impliesthatthiscapabilityisalsoafunctionofthe speedatcontactopening.Thedielectricwithstand capabilityforonecircuitbreakermayvarywithanormaldistributionandaparticularstandarddeviation. Afterre-ignition,ahighfrequencycurrentflows throughthecircuitbreaker.Theresultingarccan beextinguishedwhentheslopeofthecurrentis lowerthanthesocalledcriticalcurrentslope,a parameterthatishardtodetermine.Inthismodel, thequenchingcapabilitydielectricstrengthas measuredbyGlinkowskietal[1]isused. Thestatisticalmeanvaluesareusedinthiscircuit breakermodel.Thetestedcircuitbreakerstestdata aregroupedintothreelevels:High,medium,and lowdielectricandquenchingability.Ub / di / dt High Medium Low Aa[V/s] 1.7E7 1.30E7 0.47E6 Bb[V] 3.40E3 0.69E3 0.69E3 Cc [A/s2] -3.40E11 0.32E12 1.00E12 Dd[A/s] 255.0E6 155.0E6 190.0E6</p> <p>ThewithstandvoltageUbandthecriticalslopeof thearcquenchingcapabilitydi/dtarecalculated inthissectionusing:Aa=1.7e7,Bb=3.4e3,Cc=-3.4e11, andDd=255e6.Ifthecircuitbreakerstatistical distributionistobestudied,detailsonthismatter areexplainedin[2]. TheVacuumBreakerProbabilityofReigniting TheVCBhasaprobabilityofreignitingwhencertain operatingandcircuitparametersaremet[3].The parametersare:Theinterruptedcurrentislessthan 500to600A,thebreakercontactsmustpart0.5ms to1msbeforecurrentzerowithaspeedof1m/s,and theTRVmustrisefasterthanthebreakdownstrength ofthevacuumgap. ConditionsforOpeningoftheSwitchandthe PSCADImplementation TheconditionsforopeningtheswitchaccordingtoGlinkowskietal[1]are: Theinstantofopeningshouldbegreaterthan apre-setvalueoftopen. Theswitchisclosed. Theactualcurrentislessthanthechoppingcurrent. Thederivativeofthehighfrequencycurrent atcurrentzeroisnothigherthanthecalculated quenchingcapability. Forcreatingtheseconditions,anumberofdifferent parametershadtobecalculatedinPSCAD Themodels . intheCSMFpartoftheMasterLibrarycanbeused forsuchcalculations.Somerepresentativecalculation blocksareshowninthefiguresbelow.</p> <p>Basedontheconstants,themeanvaluesofthe dielectriccharacteristicandquenchingcritical slopecanbecalculatedby:</p> <p>Figure2 Thetopenparameteristheinstantwhenthecircuitbreaker mechanicalopeningtakesplace.Thepulsetrainisfrozenatt= topen. MechanicalopeningisinitiatedbytheMechanicalstatusswitch.</p> <p>2 PULSETHE MANITOBA HVDC RESEARCH CENTRE JOURNAL</p> <p>The Vacuum Circuit Breaker is an important circuit component in the medium voltage system due to its low maintenance cost and low environmental impact.</p> <p>Figure3 Thetchopistheinstantofcurrentchopping.Thepulse trainisfrozenatt= tchop.</p> <p>Figure4 Thecurrentslopeibdiscomparedwiththecurrent quenchingcapabilitydi/dt.Whenthecurrentslopeislessthan thequenchingcapability,parameterctrl_ibd_slope=1else0.</p> <p>Figure6 Typicalsimulationresults.</p> <p>TypicalSimulationResults Thenumberofrepeatedreignitionsdependsonmany factors;themostimportantisarcingtime(i.e.the voltagewithstandwhichhasbuiltupbetweenthe contactswhentheUtrvstartstooscillate).Italso dependsonthechoppinglevel(i.e.theenergythat istransferredfromtheinductancetothecapacitive elementsandthebreakercharacteristics). Formoredetailsaswellasforamorecompletereport, contacttheManitobaHVDCResearchCentreorthe authordirectlyatolof@karlenengineering.seReferences [1]MietekT.Glinkowski,MoisesR.Guiterrez,DieterBraun, VoltageEscalationandReignitionBehaviourofVacuum GeneratorCircuitBreakerDuringLoadShedding. Figure5 Theconditionsforopeningandclosingofthebreaker arerunthroughMonostableMultivibratorsandastandardSetand Resetlatchingcircuit.TheBRKstatusparameterisnowreflecting theelectricalstatusofthevacuumbreaker. [2]PopovMarjan,PhDThesisSwitchingThree-PhaseDistribution TransformerswithaVacuumCircuitBreakerISBN90-9016124-4. [3]SladeG.P.VacuumInterrupters:TheNewTechnologyfor SwitchingandProtectingDistributionCircuits IEEETrans.OnPowerDelivery,Vol8,No4.</p> <p>MARCH2011 3</p> <p>SinglePhaseAuto-reclosing andSecondaryArcConsiderationsJohnson Thomai, Yogesh Khanna, Shahbaz Tufail (DAR Engineering Company) Shan Jiang, Dharshana Muthumuni (Manitoba HVDC Research Centre) SinglePhasetoGround(SLG)isthemost commonfaultinpowertransmissionsystems. Singlephaseautoreclosingisusedtoimprovesystem stability,powertransfer,reliability,andavailability ofatransmissionlineduringasinglephaseto groundfault[1]. Soonafterthefault,thetwolineendbreakerswill open(faultedphaseonlyinthiscase)toisolatethe fault.However,theotherline(un-faultedphases) arestillenergized.Thereisinductiveandcapacitive couplingbetweenthefaultedlineandthehealthy phases,aswellasbetweenotherconductorsofparallel circuits(i.e.doublecircuitlines).Thiscouplinghas twoeffects[1]: 1. Itfeedsandmaintainsthefaultarc. 2. Asthearccurrentbecomeszero,thecoupling causesarecoveryvoltageacrossthearcpath. Iftherateofriseofrecoveryvoltageistoogreat, itwillreignitethearc. Thearconthefaultedphaseafterthetwolineend breakersopenisthesecondaryarc.Recoveryvoltage isthevoltageacrossthefaultpathaftertheextinction ofthesecondaryfaultarcandbeforere-closureof thecircuitbreakers. Autore-closingwillbesuccessfulonlyifthesecondary archasbeenfullyextinguishedbythetimethe breakersarere-closed.Thedurationofthesecondary arcdependsonmanyfactors.Themainfactorsare: arccurrent,recoveryvoltage,arclength,aswellas externalfactors,suchaswind.Whentransmissionlines arecompensatedwithlineendreactors,thesecondary arcextinctioncanbeimprovedbyplacingasuitably sizedneutralgroundingreactor(NGR)ontheneutral ofthelinereactors[1]-[3]. DAREngineeringhasdesignedanumberofNGRs forEHVtransmissionlinesintheGulfregion.Once theNGRparametersaredetermined,detailedelectromagnetictransientsimulationsarecarriedouton PSCAD/EMTDCtoverifytheinsulationrequirements oftheNGRandtoestimatethesecondaryarc extinctiontimesunderdifferentsystemoperating conditions.Suchinformationisessentialtoproperly designthesinglephaseautore-closerelaysettings.4 PULSETHE MANITOBA HVDC RESEARCH CENTRE JOURNAL</p> <p>TheLineEndandNeutralGroundingReactors (NGR)inEHVTransmissionLines TheNGRisused tocancelthecapacitivecomponentofthesecondaryarccurrent[1].Inordertocancelthecapacitive current,theinductiveandcapacitivebranchesmust resonate.Installationofthisreactoriseffective whenlinesaretransposed. Estimation of NGR based on the Shunt Compensation Degree TheNGRvaluecanbeestimatedbasedonthe followingdesignequations(see[2]fordetails):</p> <p>Where: B1:positivesequencelinesusceptance(Siemens); B0:zerosequencelinesusceptance(Siemens); :shuntcompensationdegree. Xr:equivalentreactanceofthelinereactor. Xn:equivalentreactanceoftheNGR Note1:B1andB0areknownfromtransmissionline characteristicsandareoutputsfromthePSCADline constantsprogram. Estimation of NGR based on the Basic Insulation Level (BIL) requirements BILisalsoaconsiderationwhen selectingtheNGR.BecausethehigherneutralBILlevel requiresspecialdesignandmoreinsulationforthe linereactor,thecostofthelinereactorandneutral reactorincreases.IfthisistheNGRdesigncriteria,the minimumacceptableBILfortheneutralpointcanbe calculatedby[4]:</p> <p>Where: BIL_N:BasicImpulseInsulationLevelfortheNGR. BIL_Ph:BasicImpulseInsulationLevelofthephase. Fora400kVsystem,theBILoftheneutralpointofthe linereactortypicallyislessthan350kV. </p> <p>OncethevalueoftheNGRisdecided(basedoneither ofthetwomethodsabove),detailedsimulations (PSCAD/EMTDC)canbecarriedouttodetermine thesecondaryarccharacteristics. TheSimulationModel Thesecondaryarcextinction timeandtherecoveryvoltagesareinfluencedbythe followingfactors: Faultlocationsonline Numberofreactors(andNGR)inservice Initialarclength Transmissionlinecharacteristicsandtransposing Arc Model ThearcmodelusedinthisPSCAD/EMTDC studyisbasedonthemodelproposedin[5].The followingparametersthatinfluencethearcextinction timeareinputstothismathematicalmodel. Initialarclength(Larc) Magnitudeoftheprimaryarc(Ip) Magnitudeofthesecondaryarc(Is)</p> <p>Initial Arc Length (Larc) Theinitialarclength influencesthesecondaryarcextinctiontime.Astime progresses,thearcelongatesfromthisinitiallength untilitisfinallyextinguished.Sincetheexactvalueof theinitialarclengthisnotapreciselyknownquantity, simulationsmayhavetobecarriedoutfordifferent practicalvalues(i.e.2m,4mand6m)beforereaching conclusionsonrelaysettings. Magnitude of the Primary Arc (Ip) Thisisthe magnitudeofthefundamentalcomponentofthe singlelinetogroundfaultcurrentataspecificfault location.Thisvaluecanbecalculatedfromfaultstudies orthroughaPSCADsimulationitself.Tocalculatethis valuefromthePSCADcircuit,thefaultisassumedto besolidwithzeroarcresistance. Magnitude of the Secondary Arc (Is) Thisisthe magnitudeofthefundamentalcomponentofthe singlelinetogroundfaultcurrentataspecificfault locationafteropeningthetwolineendbreakers.This valuecanbecalculatedfromfaultstudiesorthrough aPSCADsimulationitself.Tocalculatethisvaluefrom thePSCADcircuit,thefaultisassumedtobesolidwith zeroarcresistance.Oncethetwobreakersareopen, thephasecouplingsustainsthefaultcurrent.</p> <p>Figure1 PSCADarcmodel</p> <p>Figure2 PSCADcircuitofatransposedlinewiththearcmodel connectedtooneofthephases.</p> <p>N O V ERM B E 2 0 2 0 0 9 5 MA CHR 11 5</p> <p>Firstpeakoftherecoveryvoltage</p> <p>SimulationResults Theextinctiontimeandthe recoveryvoltageundervarioussystemoperating conditionsforfaultsona400kV/350km(approximately)doublecircuitlinearepresentedinthissection toillustratetypicalresultsthatcanbeexpected.</p> <p>RecoveryVoltage</p> <p>Figure3 Systemoperatingwithallreactorsatthelineendsubstations. FaultLocation Magnitudeoftheprimaryarc(lp)(kA) Magnitudeofthesecondaryarc(ls)(A) Extinction time(s) Larc=2.0m Larc=4.0m Larc=6.0m Recovery voltage(kV) Larc=2.0m Larc=4.0m Larc=6.0m BusA 15.2 45 0.17 0.14 0.12 46 45 63 Mid-point 5.2 37 0.14 0.12 0.12 36 30 33</p> <p>Faultoccurs</p> <p>Breakersopen</p> <p>Arcextinguishes</p> <p>Figure5 Typicalrecoveryvoltage(top)andsecondaryarccurrent (bottom)withoutthelinereactorandNGR</p> <p>References [1]E.W.Kimbark,SuppressionofGround-FaultArcsonSingle-Pole SwitchedEHVLinesbyShuntReactors,IEEETransactionsonPower ApparatusandSystems,volPAS-83,pp.285-290,March/April1964. [2]E.W.Kimbark,Selective-PoleSwitchingofLongDouble-Circuit EHVLines,IEEETransactionsonPowerApparatusandSystems, volPAS-95,pp.1,January/February,1976. [3]IEEECommitteereport,SinglePhaseTrippingandAuto-Reclosing onTransmissionLines,IEEETransactionsonPowerDelivery,vol7, pp182-192,Jan,1992. [4]M.R.D.Zadeh,MajidSanaye-Pasand,AliKadivar,Investigation ofNeutralReactorPerformanceinReducingSecondaryArcCurrent,k IEEETransactionsonPowerDelivery,vol.23,no.4,Oct2008. [5]ImprovedTechniquesforModellingFaultArcsonFaultedEHV TransmissionSystems,A.T.Johnset.el.IEEProceedings,Generation, Transmissionand,Distribution,Vol.141,No.2,March1994.</p> <p>Table1 Arcextinctiontimeandrecoveryvoltageatdifferentfault locationsunderdifferentassumedinitialarclengthvalues. Firstpeakoftherecoveryvoltage</p> <p>RecoveryVoltage</p> <p>Faultoccurs</p> <p>Breakersopen</p> <p>Arcextinguishes</p> <p>Figure4 Typicalrecoveryvoltage(top)andsecondaryarccurrent (bottom)withthelinereactorandtheNGRinservice.</p> <p>6 PULSETHE MANITOBA HVDC RESEARCH CENTRE JOURNAL</p> <p>JUNE2008 6</p> <p>KineticTurbinePowerConverterFarid Mosallat, Manitoba HVDC Research Centre KineticHydropowerisoneoftheemerging technologiesinthealternate-energypower generationsector. KineticHydropowerplants employsubmergedturbine-generatorsetstoconvert theenergyofflowingwaterintoelectricity.The producedpoweristhenusedtosupplyislandedloads orisinjectedintothegridwhereautilitynetwork isnearby. KineticTurbinescanbedeployedintidalflowsor inhigh-velocityrivers.Inriverapplications,aKinetic Turbineissubmergedandanchoredatsuitable locationsalongriverswherenaturallandtopography restrictstheflow,resultinginhighlocalvelocities. Theinitialinstallationcostanddeploymenttimeof aKineticTurbineisrelativelysmall,sinceitdoesnot requiresignificantinfrastructure,suchasadamor apowerhouse.Therefore,suchsetupscanberelatively inexpensiveandareexpectedtohaveminimal environmentalfootprint. Harnessingoftheenergyinwatercurrentsissimilarto convertingthewindenergyintoelectricity.Incontrast towind,however,waterflowvariationsaresteadier andmorepredictable.Moreover,thedensityofwater isover800timeslargerthanthatofair.Thiseffectsa vastdifferencebetweenpowerdensitiesofflowing waterandwind.Forinstance,thepowerdensityof waterflowingat4m/s,anupperrangeforrapidwater currents,correspond...</p>